Control of cytodifferentiation by extracellular matrix (ECM) will be studied in the following ways: the part of the collagen molecule responsible for stimulating differentiation of the embryonic chick corneal epithelium will be analysed by substituting collagen fragments and synthetic polypeptides for intact lens capsule. Relation of ECM to the cell surface will be studied by analysing the morphology and distribuion of ECM on the corneal epithelial cell surface (using lectins and stains and both scanning and transmission electron microscopy) and by examining the cell membrane in freeze fractures. BIBLIOGRAPHIC REFERENCES: Nist, C., von der Mark, K., Hay, E.D., Olsen, B.R., Bornstein, P., Ross, R. and Dehm, P. 1975. Localization of procollagen in chick corneal and tendon fibroblasts by ferritin conjugated antibodies. J. Cell Biol. 65:75-87. Hay, E.D. and Coward, S.J. 1975. Fine structure of planaria. I. Nature of the "neoblast." J. Ultrastruct. Res. 50: 1-21.